1. Field of the Disclosure
The present disclosure is related to vehicular and mechanical applications, including automotive, truck, carts, ATVs, and other applications that utilize flexible covers, known as boots, to protect constant velocity (CV) joints and other types of bearing assemblies that are found in the drive train or suspensions of vehicles.
2. Description of the Related Art
A great number of cars, trucks and other vehicles use CV johns and other bearing assemblies to help transfer power through the transmission or drive train to the drive wheels. Front wheel drive vehicles and some rear wheel drive vehicles that use transaxles with half shafts, or half axles, to transfer power to the drive wheels, is one typical application. As an example, a front wheel drive car is commonly configured with two half shafts to connect the transaxle to the drive wheels. The interfaces of the half shafts to the transmission and to the drive wheels are commonly protected by a flexible boot made of rubber or other flexible material.
These boots are installed onto a half axle or similar assembly before the half axle is installed connecting the transaxle to the hub of the drive wheel. On the transaxle side, the end of the half shaft is typically a spline shaft protected by a flexible boot that is banded or clamped to the half shaft. On the wheel side, the end of the half axle contains a CV bearing joint that is protected by a similar flexible boot. The CV boot, as it is commonly called, is banded or clamped to the half axle and the wheel hub to seal in lubrication for the CV bearing joint and to keep unwanted contamination from entering the CV joint.
A CV joint is a rugged bearing joint that can last for hundreds of thousands of miles if properly sealed and lubricated. On the other hand, the protective boots typically fail after 50,000 to 100,000 miles or even sooner depending on driving conditions and exposure to other conditions or hazards that tend to break or rupture the protective boots. After the protective boot is compromised, the CV joint or other hearing type or moving joint can fail quickly once exposed to water, dirt, dust, and other contaminants.
When the protective boot is broken or compromised, the most elaborate and expensive repair involves disassembly and replacement of the half shaft with a new or remanufactured half shaft with new protective boots.
In other cases where the boot has been compromised but the bearing joint or CV joint is still functioning adequately, the damaged boot can be removed, the joint can be cleaned, re-lubricated, and another protective boot can be installed. For this type of repair, with a specially designed “split boot,” the half shaft can remain in place, which reduces the parts and labor costs of the required repair.
To this end, there are two styles of split boots that are available on the market for protective boot replacement. There are also designs that have been presented for a third style of split boot with a zipper, but none of these prior zipper designs have ever been produced, to our knowledge. The first of the two styles involves a rubber or other flexible material that is made with a split or axial slit in the boot to allow installation of the protective boot over the half shaft while the half shaft remains in place (connected at both ends). This style requires very small nuts and bolts that catch small tabs along the split to hold the seam together once the boot is installed onto the half shaft, Once the seam is bolted up, the split boot is clamped on both the half axle side and the wheel or transaxle side to finish the protective sealing of, the joint.
The biggest drawback with this style of boot is that the bolted split or seam is typically not a good environmental seal since the seam or split tends to somewhat pull apart during use due to the required flexing of the protective boot. Thus, the joint lubrication and outside contamination can both move through the split, which leads to premature bearing or CV joint failure.
The second of the two styles has a split protective boot that is available on the market is a protective boot made in two halves with tongue and groove joints that are glued together with a permanent adhesive to seal the axial boot seam. This style of boot is typically a less flexible, more plastic like material that better facilitates the required gluing process. A typical installation scenario for this style of boot is to glue one of the split seams together, then install the split CV boot onto the half shaft with the remaining seam open, then glue the remaining seam together once the CV joint or bearing joint has been cleaned and re-lubricated.
While this style of split boot can result in a more environmental seal on the boot splits or seams as compared to the bolted seam split boot, it also has some notable installation and usage limitations. First, with the new grease in the bearing or CV joint and in the presence of other containments on the half shaft and in the area of the installation of the split boot, it is difficult to keep the remaining split seam free of grease, dirt, and other contaminants to allow the gluing operation to result in a good seal for the seam. If the seam is contaminated, the glue or adhesive will not properly adhere to the boot material to allow the split or seam to be successfully sealed. On some vehicles, there may be enough space to glue the remaining seam first, then, pull the boot back to grease the joint, but this may not always be the case. After the joint is greased and the boot is positioned, the boot is then clamped on both ends.
Before the boot is clamped, the multiple gluing operations for this style of split seam boot significantly slows the installation process as compared to the bolted seam type, thereby adding to labor costs. The other limitation of this style is that the material is harder and less flexible making the process of banding or clamping both ends of the boot, to complete the installation, more difficult. It is not uncommon for one or both of the end clamps to move or not seal as well as the more flexible bolted style split boot noted above. Another risk of lubrication loss or joint contamination is through the end seals of this style of boot.
In summary, neither of the available split boot designs discussed above are ideal for ease of installation and long term protection of a Constant Velocity (CV) joint and/or a bearing joint. It can be seen, then, that there is a need in the art for a different, more producible split boot design with a zipper closure to install or replace new or broken CV boots and other similar boots that protect similar interfaces or bearing assemblies while avoiding the cost of a complete removal, replacement, and reinstallation of a half shaft or other larger sub-assembly.